Transposition of the Great Arteries
Abnormal anatomic relationship between the great arteries and the ventricles in which the aorta arises from the anatomic right ventricle and the pulmonary artery arises from the anatomic left ventricle
Incidence is 20 to 30 per 100,000 live births, with a 60–70% male predilection.
Transposition of the great arteries (TGA) represents up to 7% of all cases of congenital heart disease.
- Systemic and pulmonary circulations are separated and function in parallel.
- Desaturated systemic venous blood is ejected from the right heart to the aorta, whereas the oxygenated pulmonary venous blood is ejected from the left ventricle into the lungs.
- Degree of hypoxemia depends on amount of intercirculatory mixing (patent ductus arteriosus [PDA], patent foramen ovale [PFO], ventricular septal defect [VSD]).
- Degree of left-to-right shunting is the effective systemic blood flow, whereas right-to-left shunting determines effective pulmonary flow.
- PDA and PFO with intact ventricular septum (50%)
- VSD (40%)
- Posterior malalignment VSD with left ventricular outflow tract obstruction (e.g., subpulmonic stenosis, pulmonary stenosis, pulmonary atresia) (10%)
- Anterior malalignment VSD with right ventricular outflow tract obstruction (e.g., subaortic stenosis, aortic stenosis, coarctation of the aorta, or interruption of the aortic arch) (10%)
- Leftward juxtaposition of the atrial appendages (5%)
- Straddling of the atrioventricular valve
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